Carlos R. de Carvalho

A proposal to introduce a topic of contemporary physics into high-school teaching

This article presents an approach to integrate contemporary physics into high-school teaching. We present a simple way to understand mass spectroscopy using basic physics concepts, so that high-school students may have contact with recent topics of modern research. The main features of a time-of-flight (TOF) mass spectrometer using secondary school physics concepts are discussed. The use of home-made apparatus is described. Some results obtained with CsI samples showing the dependence between mass and TOF are presented.

Nonprobabilistic teleportation of a field state via cavity QED

In this paper, we discuss a teleportation scheme of coherent states of a cavity field. The experimental realization proposed makes use of cavity quantum electrodynamics, involving the interaction of Rydberg atoms with micromaser and Ramsey cavities. In our scheme the Ramsey cavities and the atoms play the role of auxiliary systems used to teleport the state from one micromaser cavity to another. We show that, even if the correct atomic detection fails in the first trials, one can succeed in teleportating the cavity field state if proper measurement occurs in a later atom.

Toward a test of angular-momentum coherence in a twin-atom interferometer

We present a scheme well-suited to investigate quantitatively the angular momentum coherence of molecular fragments. Assuming that the dissociated molecule has a null total angular momentum, we investigate the propagation of the corresponding atomic fragments in the apparatus. We show that the envisioned interferometer enables one to distinguish unambiguously a spin-coherent from a spin-incoherent dissociation, as well as to estimate the purity of the angular momentum density matrix associated with the fragments. This setup, which may be seen as an atomic analogue of a twin-photon interferometer, can be used to investigate the suitability of molecule dissociation processes -- such as the metastable hydrogen atoms H(

New experiment for coincidence detection of H(2l)+H(2l') coming from dissociation of H2 induced by electron impact

2^2 S

Laser interaction with a pair of two-dimensional coupled quantum dots

)-H(

Negative ions and their behavior in collisions

2^2 S

Phase-space reconstruction of an atomic chaotic system

) dissociation - for coherent twin-atom optics.

Electron-detachment cross section for CN − and O 2 − incident on N 2 at intermediate velocities

In this work we present a new experimental apparatus being set up in Rio de Janeiro to study coincidence detection of pairs of excited hydrogen atoms coming from the dissociation of a single H2 molecule by detecting emitted Lyman-alpha radiation.

On the working conditions of a two-pan balance

We study the effects of a laser on the splitting of the lowest electronic states of a pair of two-dimensional (2D) GaAs-(Ga,Al)As coupled quantum dots, in the presence of a homogeneous external magnetic field. The interaction of light with the 2D quantum dots is treated within a dressed-band approach in which a two-band scheme is used to model the GaAs bulk semiconductor whereas the interaction with the laser field is treated through the renormalization of the semiconductorenergy gap and conduction/valence effective masses. This approach is valid far from resonances and has been successfully used to treat other confined semiconductor heterostructures. We focus our attention on the splitting of the lowest singlet and triplet states and on their double occupation probability. We analyze the exchange coupling (J) in the effective Heisenberg model as a function of the laser field and its detuning, as well as of the magnetic field (B) within the Heitler-London approximation of molecular physics. We find that due to the electronic confinement the laser may play a role similar to the external magnetic field in the qualitative behavior of the exchange parameter J. Furthermore, the presence of the laser may assure both the sizable exchange coupling and the vanishingly small double occupation probability required for efficient quantum computer operations, even in the absence of an external magnetic field. Besides being of fundamental interest, these features may be used as an efficient two-qubit gate control.